# Which solution is more concentrated?2.7 L of solution containing 3.0 mol HCl or 120 ml of solution made by dissolving 3.0x10^22 molecules of HCl The working out is necessary, I am unsure of how to...

Which solution is more concentrated?

2.7 L of solution containing 3.0 mol HCl or 120 ml of solution made by dissolving 3.0x10^22 molecules of HCl

The working out is necessary, I am unsure of how to work it out, I already have the answer though. Thanks

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jeew-m | College Teacher | (Level 1) Educator Emeritus

Posted on

I think the question should be modified in the end part. It should not be 3.0x10^22 molecules. It should be 3.0x10^22 particles of HCl.

Otherwise You will have a HCl concentration which you will never achieve in the sample.

`HCl_(aq)-------gt H_(aq)^++Cl_(aq)^-`

HCl is completely dissolve in water. So we get `H^+` moles equal to the HCl moles we pu in water.

For the first one we have 3 mol of HCl in 2.7 liters of water.

Concentration is defined as the amount of moles in 1 liter of water.

So its `H^+` concentration = 3/2.7 mol/l

= 1.1111mol/l

For the second one 3.0x10^22 particles HCl dissolved in 120ml of water.

In Avagadro law he has indicated that a mole of a substance has 6.022xx 10^-23 particles.

So number of moles in second solution =3.0x10^22 /6.022xx 10^-23

= 0.498xx10^-1

= 0.05mol

So the H^+concentration in second solution = 0.05/120*1000 mol/l

= 0.4167 mol/l

So First one has more H^+ concentration.

Sources:

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